The present invention relates to the field of seismic cable repair. More particularly, the present invention relates to an apparatus and method for facilitating in-water seismic cable repair at an offshore survey location.
Marine seismic cables known as streamers are towed behind seismic vessels to collect data related to subsurface geologic formations. The streamers typically include communication lines for transmitting signals, cable stress elements for providing strength, and hydrophones for detecting seismic waves reflected from the geologic formations.
Seismic cables are normally constructed by joining multiple cable sections with multiple connecting modules. Each cable section is typically one hundred meters long, and a streamer cable is typically 4000 to 8000 meters long. The connecting modules, constructed with titanium or stainless steel, provide a waterproof seal between adjacent cable sections. When a seismic cable section needs to be replaced because of damage or a failure, the cable section must be detached from adjacent connecting modules so that a new cable section can be installed.
Historically, marine seismic repair has been performed by stopping the tow vessel and by removing the entire streamer cable from the water. The streamers are retrieved onto the vessel deck, a new cable section is substituted for the damaged cable section, and the entire seismic cable is re-deployed into the water behind the tow vessel. Deck site repair is typically performed because of the difficulty and potential hazards of in-water seismic cable repairs.
Conventional deck site repair of seismic cables slows seismic operations and increases operation cost. Seismic cable repair causes significant down-time expense because the seismic operations necessarily cease during repair operations. The replacement of a single seismic cable section can require a number of days. Additionally, tow vessel movement and cable handling equipment can stretch and break seismic cables, thereby increasing the overall cost and delay of seismic cable repairs. Accordingly, a need exists for an improved apparatus and method for facilitating in-water repair of damaged seismic cable sections.